The present invention relates to method and apparatus for applying an elastic band onto a moving web and more particularly to method and apparatus for intermittently applying pieces of elastic band severed into a predetermined lengths, at least partially displacing said pieces laterally of the direction in which said web travels, onto said web thus continuously forming a plurality of articles which can to be severed into said individual articles. This method and apparatus can be used as an effective technique for applying elastic band onto various garments such as disposable diapers, diaper-covers and training pants.
For garments such as disposable diapers, various techniques are already been known for applying an elastic band onto the openings surrounding the legs and waist of the user for fitness.
Japanese Patent Publication No. 57-26219 discloses a technique such that a continuous elastic band is applied with adhesive at regular intervals along its longitudinal direction while said continuous elastic band is maintained in a stretched condition, said continuous elastic band being bonded onto said continuous web with said adhesive, said continuous elastic band being severed at non-bonded portions that are not applied with adhesive and at the same time said non-bonded portions are allowed to contract so as to make these portions non-functional, and thereby said elastic band is intermittently bonded onto said web. According to this technique of the prior art, however, said non-functional portions are wasteful and, in addition, said non-bonded portions are left to contract inwardly after the elastic band has been bonded onto the web, and this contraction of said non-bonded portions forms undesirable openings at the ends of the finished article through which leakage of excretion occurs.
Japanese Disclosure Gazette No. 58-174603 discloses a technique in which a continuous elastic band is applied with adhesive at regular intervals along its longitudinal direction while said continuous elastic band is maintained in a stretched condition, said continuous elastic band being fed onto the peripheral surface of a rotatable suction drum, said continuous elastic band being severed at portions applied with no adhesive and at the same time the portions with no adhesive applied are left contract to make these portions non-functional, then this discontinuous elastic band is transferred onto the continuous web and thereby said elastic bend is intermittently bonded onto said web. This technique certainly avoids the formation of undesirable openings at the ends of the finished article but the problem of waste remains unsolved.
Japanese Disclosure Gazette No. 58-180601 discloses a technique wherein a continuous elastic band is continuously or intermittently applied with adhesive and then fed onto the peripheral surface of a rotatable suction drum, said elastic band being severed on said rotatable suction drum into predetermined lengths, each severed piece of elastic band is held on said peripheral surface of said rotatable suction drum, each piece of elastic band is moved along with said peripheral surface but the following continuous elastic band is made to slide relative to said peripheral surface so that the rear end of said severed piece of elastic band is spaced from the front end of the following continuous elastic band, then said severed piece of elastic band is held on said peripheral surface of the rotatable suction drum and moved along with said peripheral surface but the following continuous elastic band is made to slide relative to said peripheral surface so as to space the rear end of said severed piece of elastic band from the front end of said following continuous elastic band, then said severed piece of elastic band is transferred onto said web, and thereby said elastic band is intermittently bonded onto said web. According to this technique, however, a control of said slippage and a suction pressure inevitably involves unreliable technical factors even though said formation of undesirable openings due to contraction of the non-bonded portions at the ends of the finished article can be avoided and the intermittent application of adhesive onto the continuous elastic band is not required. In view of such limitations, this technique of the prior art is not suitable for bonding the continuous elastic band onto said web at a high rotational speed.
A technique for bonding the elastic band onto the web so that the individually severed pieces of said elastic band have predetermined curved orientations on said web is well known, for example, from Japanese Disclosure Gazette No. 61-162462. However, according to this technique, mechanisms constituting the respective means to space the respective severed pieces of elastic bands from one another on the rotatable device, to hold said elastic band, to displace said elastic band laterally of the direction in which the web travels and to transfer said pieces of elastic band are so complicated that this technique is not suitable for bonding the elastic band onto the web in view of speed, reliability and efficiency of the various mechanisms included in the apparatus.
Accordingly, a primary object of the present invention is to provide a technique for intermittently bonding elastic band onto a web at predetermined positions at high speed, reliability and efficiency through a continuous operation including the step of holding said elastic band, particularly holding said elastic band while at least partially displaced laterally of the web, if desired, so as to apply said elastic band onto said web in such orientation.